Insulated accelerating pump



Jan. 5, 1960 o. o; NEWMAN 2,919,903

INSULATED ACCELERATING PUMP Filed Dec. 27, 1956 INVENTOR.

ODUS O. NEWMAN ATTORNEY United States Patent O INSULATED ACCELERATING PUMP Odus O. Newman, St. Louis, Mo., assignor to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Application December 27, 1956, Serial No. 630,934

2 Claims. (Cl. 261-34) This invention relates to carburetors for internal combustion engines and more particularly to a carburetor of the type provided with an accelerating pump adapted to eject a stream of fuel into a mixing conduit to supplement the quantity of fuel supplied from the main fuel nozzle during opening movement of the throttle valve.

During hot weather, gasoline in a conventional accelerating pump chamber and the outlet passage leading therefrom to the mixing conduit becomes heated and tends to percolate, thereby causing the formation of gas bubbles which force the fuel through the outlet passage into the mixing conduit when the engine is stopped or idling, and which also reduce the efficiency of the pump when the throttle is opened during acceleration.

For operation of the pump at maximum efficiency, the fuel in the pump chamber and outlet passage should be in a solid liquid condition to cause the fuel to be projected in the form of a continuous, uninterrupted stream through a restricted outlet nozzle into the mixing conduit to provide uniformly increasing acceleration of the engine. It is, therefore, an object of this invention to provide a carburetor accelerating pump structure adapted to operate at maximum efficiency during acceleration of an engine.

Another object of the invention resides in the provision of a carburetor accelerating pump structure adapted to project a continuous, uninterrupted stream of solid liquid fuel into the mixing conduit during acceleration of an engine.

A further object of the invention resides in the provision of a carburetor accelerating pump structure provided with a heat-insulated pump cylinder to reduce the transmission of heat to the fuel in the pump chamber.

Another object of the invention resides in the provision of an accelerating pump structure embodying a pump cylinder formed from a suitable thermoplastic or thermo-setting plastic material to provide an insulating chamber in the wall thereof to decrease the coefficient of heat transmission through the cylinder wall to the fuel in the pump chamber.

The invention embodies other novel features, details of construction and arrangement of parts which are hereinafter set forth in the specification and claims and illustrated in the accompanying drawing, wherein:

Fig. l is a vertical sectional view illustrating a carburetor provided with an accelerating pump embodying features of the invention.

Fig. 2 is a detail transverse sectional view of the pump cylinder.

Referring now to the drawing for a better understanding of the invention, a carburetor is shown as comprising a downdraft mixing conduit or passage 6 having inner and outer venturis 7 and 8, respectively, and a throttle valve 9 by means of which the normal supply of fuel to the engine is induced to flow through one or more main fuel ports 11 or idle ports 1'12 in accordance with well known principles of carburetion. Fuel is supplied to the 2,919,908 Patented Jan. 5, 1960 ice main fuel port 11 and idle ports 12 through passages (not shown) leading from a constant level fuel bowl 13. A conventional float (not shown) is secured to a float arm 14 pivotally mounted at 16, the arm being formed with a finger 17 to engage and control the movement of the needle 18 of a fuel inlet valve 19 to regulate the flow of fuel into the fuel bowl. The carburetor is provided with a choke valve 21 which may be manually or automatically controlled in accordance with conventional practice.

The carburetor is provided with an accelerating pump structure which is shown as comprising a cylinder 22 having a piston 23 mounted for reciprocative movement therein responsive to movement of the throttle valve 9. A fuel inlet passage 24 leads from the fuel bowl 13 to the cylinder 22, and a fuel outlet passage 26 leads from the cylinder to an outlet nozzle 27. Check valves 28 and 29 are provided in the inlet and outlet passages 24 and 26, respectively.

A piston rod 31 is secured at one end thereof to the piston 23' and has its other end formed with a slot 32 to receive one end of Ia lever 33 pivotally mounted intermediate its ends on the carburetor housing 34. The other end of the lever 33 is connected by means of a link 36 to a lever 37 fixed on one end of the throttle shaft 38. A compression spring 39 is interposed between the piston 23 and the fuel bowl cover 41 to yieldably resist upward movement of the piston responsive to closing movement of the throttle valve. The throttle valve is adapted to be opened or closed by any conventional means operative responsive to movement of an accelerator pedal (not shown).

The carburetor housing 34 is formed with an air bleed passage 42 leading from the inlet end of the mixing passage 6, anterior to the choke valve, and terminating at a trough-shaped chamber 43 disposed between` the outer nozzle 27 and a wall portion 44 of the mixing passage 6. A port or window 46 is formed in the wall portion 44 in axial alignment with the outlet nozzle 27 for the passage of streams of fuel ejected from the nozzle responsive to downward movement of the piston 23 in the cylinder 22. As the throttle valve 9 is opened, air is drawn through the air bleed passage 42 and then through the window 46 to mix with the stream of fuel ejected from the nozzle. ln order to properly mix the stream of fuel from the nozzle 27 with the air passing through the mixing passage 6, the stream of fuel is projected against the outer side of the inner venturi 7 to form a spray.

Due to hot weather and heat radiated from the engine, fuel within the cylinder 22 and outlet passage 26 tends to percolate and causes the air chamber 43 to become filled with fuel when the engine is stopped. Upon starting of the engine, fuel ejected from the nozzle 27 then merely passes into the chamber 43 to cause the fuel therein to dribble through the window 46 and thence along the wall of the mixing passage 6, thereby greatly impairing the usefulness of the accelerating pump. To correct this objectional condition, the air chamber 43 is provided with a small drain passage `47 leading therefrom to the mixing passage, whereby 'any fuel which percolates into the chamber is quickly drained into the mixing passage to prevent interference with streams of fuel being ejected from the nozzle 27, as shown, described and claimed in a copending application, Serial No. 611,620, led September 24, 1956, in the name of lames F. Armstrong, now abandoned.

To insulate the fuel in the pump chamber 51 from heat to reduce or prevent percolation, the cylinder 22 is shown as formed of a suitable plastic material which is resistant to gasoline and has a relatively low coefficient of heat conductivity, such as nylon, glass, or one of the thermosetting plastics comprising phenol-formaldehyde resins, such as Bakelite.

To further insulate the fuel in the pump chamber 51 from heat, the cylinder 22 is formed with inner and outer cylindrical side walls 52 and 53, respectively, merging with a bottom S4 and provided with a ring-shaped cap 56 to define a dead air chamber 57. The cap 56 is secured in fixed position to the upper ends of the side walls 52 and 53 by a suitable cement.

The bottom 54 is formed with a cylindrical boss 58 secured in a cylindrical recess 59 in the carburetor bowl 13 by means of a suitable cement. It will be noted that portions of the fuel passages 24 and 26 adjacent the pump chamber 51 are formed in the boss 58 to insulate the fuel therein from heat from the engine.

In the operation of the carburetor thus described, opening movement of the throttle valve 9 permits the compression spring 39 to move the piston 23 downwardly in the cylinder 22 to cause fuel to be ejected in a stream from the nozzle 27 through the window 46 and against the outer side of the inner venturi 7 to form a spray of fuel adaptedto mix rapidly with the air passing through the mixing passage 6 and air bleed passage 42 to insure proper acceleration of the engine. During closing movement of the throttle valve, the piston 23 is retracted to compress the spring 39 and to draw fuel from the fuel bowl 13 into the cylinder 22.

Certain structures have been described herein which will fulfill all the objects of the present invention, but it is contemplated that other modifications will be obvious to those skilled in the art which come within the scope of the invention as defined by the appended claims.

I claim:

1. In a carburetor including a fuel bowl, said fuel bowl being formed with a recess in its bottom portion, a body defining a mixture conduit, an accelerating pump for delivering fuel to the mixture conduit including a pump body with a pumping chamber and an integral base portion adapted to seat in said recess in said bowl, said accelerating pump body being formed of plastic material having a relatively low coecient of heat conductivity, the chamber in said pump body being provided with inner and outer spaced apart walls defining a dead air space adjacent the body defining the mixture conduit, the outer of said walls being also spaced from said body defining the mixture conduit and located within said fuel bowl for reducing the amount of heat transmitted from the engine by conduction to said pump body and to permit contact of the fuel in the bowl with said wall so that pump wall temperature is no higher than fuel temperature.

2. in a carburetor including a fuel bowl and a body defining a mixture conduit, an accelerating pump for delivering fuel to the mixture conduit arranged in the fuel bowl, said accelerating pump comprising a casing of a plastic material having a relatively low coeicient of heat conductivity, said casing having inner and outer spaced walls adjacent the body defining the mixture conduit to provide a dead air chamber therealong for reducing the amount of heat transmitted from the engine, said outer wall being positioned for contact with the fuel in the fuel bowl so that pump wall temperature is no higher than fuel temperature.

References Cited in the file of this patent UNITED STATES PATENTS 1,933,389 Prentiss Oct. 31, 1933 2,054,363 Croon Sept. 15, 1936 2,340,820 Moseley Feb. 1, 1944 2,515,956 Greenberg July 18, 1950 2,698,700 Grosh Jan. 4, 1955 

